U.S. Pat. No. 4,445,856 refers to a method and device for mutual alignment of the chewing surfaces of the upper jaw and the lower jaw for the purpose of producing dentures.
For this a fork-like bag made of plastic material is utilized which is preferably filled with creamy gypsum and which is then interposed between the teeth or, respectively, between provisional prostheses made of wax. The patient bites on the liquid wadding with a moderate force with the wadding being filled to an extent to just prevent a mutual contact of the teeth. The teeth rather float with respect to each other, but do not mutually engage. As long as the gypsum is still liquid, the patient has the possibility to laterally move the lower jaw in a testing manner to find out on a most convenient position of the lower jaw in which exerting biting force is sensed to meet the smallest resistance. Once this particular position is found the patient keeps it until the gypsum hardens. The shape of the hardened bag accurately corresponds to the physiologically proper mutual alignment of the chewing surfaces of the upper and lower jaw.
The method of the patent referred to avoids substantial disadvantages of other known registering methods. This particularly applies to methods which utilize one or more supporting pins provided at the provisional prosthesis for registering the position between the upper and lower jaw. Such method is complicated. Furthermore, a correction of the position of the lower jaw after brought into contact with the upper jaw cannot be obtained free of interference, since a free interplay of the jaws to find the proper alignment is not possible. In utilizing a wax impression, where the patient bites on a piece of wax which after warming is interposed between the teeth, any correction in position of the lower jaw with respect to the upper jaw is not possible since the wax obstructs a free sliding motion.